[HighAltitude]

I'm still spinning my wheels trying to use advanced flight modes. 
Vehicle - S450 frame, Multistar 2216-800 motors, Afro 20 A ESC's with Simon K firmware (version unknown), Revo board mounted on upper deck of frame with 40mm spacing from lower deck/PDB, Orange R1020X V2 RX using PWM via FlexiIO port, OP Mini GPS on Main port, onboard Mag. 
GCS version - Librepilot 16.09-RC2
It flies nicely under manual control when I enable one flight mode with all the default values.
I've set the home location and calibrated all the sensors without apparent problems. INS13 is enabled. 
When I set up 3 flight modes: Mode 1 with the default values, Mode 2 to Velocity Roam, and Mode 3 to Position Hold, my usual arming process (zero throttle/right yaw) doesn't arm the motors.
I'm doing this indoors since it's too cold (+10 F) outside, so there's no GPS fix, but I can get 8-12 satellites when I do venture outdoors.  My batteries obviously don't like that temperature, so time outside is limited. 
Magnetometer setting is onboard only, Mag type Flexi.
Magnetometer status says "Source Invalid" with the Mag Alarm window showing values fluctuating around 20% with no flight battery connected and around 13% connected but motors idle. Power leads from ESC's to motors are twisted but from PDB to ESC's too short to twist.
Questions:
1. What does the % in the Mag Alarm window mean?
2. Does the board need a valid GPS fix and magnetometer data to allow arming?
3. Any other advice?
Thanks
 

[f5soh]

1. What does the % in the Mag Alarm window mean?

The percentage show the error between the expected mag vector length (for your Home position) and the measured vector length from Mag sensor.

2. Does the board need a valid GPS fix and magnetometer data to allow arming?

Yes, needed.

[Mateusz]

3. Re

• Magnetometer must be calibrated outdoors (far from metallic objects) and always green to fly reliably
• INS13 uses all sensors with no exception, so all must be calibrated properly this includes functional mag, gps and solid altitude hold with baro (altitude hold is different thing then position hold) .
• Temp calibration is for both gyro and baro (baro light sensitive, gyro motion sensitive) so board must be motion-less and in darkness.
• INS13 is not meant for flying indoors